Telephone system



R. S. WILBUR AND W. H. HARRISON. TELEPHONE SYSTEM.

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BAY S. WILBUR, OF LYNDHURST, NEW JERSEY, AND WILLAIVE H. HARRISON, OF

BROOKLYN, NEW YORK, ASSGNORS T0 WESTERN ELECTRIC COMPANY, IN GOR- PORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Apr. 20, 1'920.

Application filed october 17, 1918. Serial No. 258,505.

T 0 all whom t may concern Be it known that we, RAY S. vl/*ninna and VILLIAM il. HAnRisoN, citizens oit the United States, residing at Lyndhurst, in the county of Bergen, State or" New Jersey, and at Brooklyn, in the county ot Kings, State oi New York, respectively, have invented certain new and useful Improvements in Telephone Systems, ot which the following is a full. clear, concise, and exact description.

rlhhis invention relates to telephone systems and more particularly to such systems in which trunk lines common to a plurality or" switchboards may be employed in establishing` connections between telephone lines terminating at the various switchboards.

The obi ect oit this invention is to provide a system ot this character in which a limited number oi trunk lines may be more efficiently used to-supply a large number of channels for telephone communication between the various switchboards connectible with the trunk lines.

in accordance with the various features ot this invention, two trunk lilies connecting together two widely separated switchboards pass through a plurality ot intermediate switchboards, apparatus being` provided at each intermediate switchboard by means of' which connection may be established between any telephone line terminating` therea-t and a switchboard in either direction over either trunk line or over a phantom circuit formed of the two trunk lines. Normally the two trunk lines and the phantom circuit superposed thereon are looped through each intermediate switchboard. and when connection is with either trunk line at any such switchboard, that trunk line is severed at that switchboard and apparatus functions to maintain the continuity ot the phantom cicuit through that switchboard. Likewise, it connection be made with the phantom circuit at an intermediate switchboard, the phantom circuit is severed at that switchboard and apparatus functions to maintain the continuity ot both trunk lines through that s ltclcihoard.

For a more complete understanding ot this invention, reference should be had to the tollowii f description considered in connection with he accoiniianying drawings illustrating one embodiment thereoi", and in which Figure l shows two trunk lines joining two widely separated switchboards and passing through a plurality of intermediate switchboards, the two trunl: lines being` phantomed at each ot the terminal switchboards to provide a phantom circuit therebetween; Fig. 2 shows a telephone line of the type terminating at the intermediate switchboards and a link circuit of' the type employed :tor interconnecting telephone lines or for connecting a telephone line with either oi the trunk lines or with the phantom circuit; and Fig. 3 shows the organic/.ation of apparatus and circuits employed at each of the intermediate switchboaiwils.

Referring more particularly to l. 5 and G represent two trunk lines joining; two terminal switchboards A and B. T ie trunk line terminates in a jack 7 at the switchboard A and in a jack S at the switchlgioard B, while the trunk line 6 terminates in a jack 9 at the switchboard A and in a jack l() at the switchboard B. ln order that a phantom circuit between the terminal switchboards may be superimposed upon the trunk lines 5 and 6, repeating coils ll are connected in each trunl line at each of the terminal switchboards. This phantom circu terminates at the switchboard i in a. jack l2 connected to the middle points of windings of the repeating coils il, il. thereat. while at the switchboard B the phantom circuit terminates in a jack similarly connected to the middle points` oi the repeating coils ll, ll thereat. Associated t ith each of the jacks is a ring-up relay lll which is cnergized by means ot ringingr current incorning over the respective trunk line or phantom circuit, and when energized lookin up through the lower normal contact ot the jack and the contact o'l' the relay thereirv to light a line lamp l5, and maintains the lamp lighted until connection made with the corresponding aeg, whereby the normal contacts of the ack are opened to release and disconnect the relay from the line and to extinguish the lamp. In Fig. l the apparatus shown to the lett oi dotted line i.; located at the switchboard A., while shown to the right ot the dotted li* e 2,--2

located at the switchboard B.

As hereinbefore stated, the trunk lines 5k and 6 and the phantom circuit superimposed thereupon are looped through a plurality of intermediate switchboards. In Fig. l these are represented by the letters X, Y and Z. All of these intermediate switchboards are identically equipped.

The circuits. and apparatus of an intermediate switchboard associated with the trunk lines and phantom circuit are shown in Fig. 3, while in Fig. 2 there are shown a telephone line C representing the type of telephone line terminating at each of the intermediate switchboards and a cord circuit D representing the type of cord circuit employed at each of the intermediate switchboards for interconnecting telephone lines and for connecting telephone lines with the trunk lines and the phantom circuit.

The trunk lines and the phantom circuit are normally looped through each of the intermediate switchboards without being connected with any of the apparatus thereat. For example, trunk line 5 enters an intermediate switchboard `lrom the lett, through the normal contacts of relay 20 and extending over conductors `21 and 22 and passing from the intermediate switchboard through the normal contacts oi relay 23 and then on to the next switchboard. ln like manner, trunk line 6. enters an intermediate switchboard through the normal contacts of relay 24, extending therethrough over conductors 25 and 26 and out through the normal contacts of relay 27. ln order that connection may be made with either of the trunk lines or with the phantom circuit at an intermediate switchboard, there are associated with the trunk line 5 a jack 30 for establishing connection therewith in one direction and a jack 31 for establishing connection therewith in the other direction; with the trunk line 6, a jack 32 for establishing connection therewith in one direction, a jack 33 for establishing connection therewith in the other direction; and with the phantom circuit a jack 34 for establishing connection therewith in one direction and a jack 35 iior establishing connection therewith in the other direction. Jacks 36 and 37 associated vwith the trunk lines 5 and 6 respectively and a jack 38 associated with the phantom circuit are test jacks by means of which the operator thereat, upon connecting the cord circuit D therewith and actuating the listening key, may bridge the operatons telephone set across the corresponding trunk line or phantom circuit to determine whether the particular trunk line or phantom circuit is idle or busy. i

In order that the continuity of the phan- I tom circuit through an intermediate switchboard may be maintained when connection thereat is made with either of the trunk lines, repeating coils are associated with each of the connection jacks for the trunk lines. rlhese repeating coils perform the further function of connecting the jack terminals with the trunk line. Onev side of each of these repeating coils 40 is connected with the tip and ring contacts of the associated jack, while the other side thereof is connected to normally open contacts of the associated switching relay through whose normal contacts the trunk line enters or leaves the intermediate switchboard. There is associated with each of the phantom circuit jacks 34 and 35 a. repeating coil 41, one side of which is connected to the tip and ring contacts of the associated jack and the other side of which is connected to normally open contacts of a switching relay. The repeating coil associated with jack 34 is connected with the normally open contacts of switching relay 427 and the repeating coil associated with jacl; 35 is connected with the normally open contacts of switching relay 43.

In order that the operator at 'an intermediate switchboard may be signaled over either of the trunk linesor over the phantom circuit, telephone call bells of the usual construction are associated with the trunk lines and phantom circuit. Call bell 45 is normally bridged across looping conductors 2l and 22 of the trunlr line 5 through normally closed contacts 46. and 47 of a switching relay 48, while call bell 46 is normally bridged across the looping conductors 25 and 26 of the trunk line 6 through normally closed contacts 49 and 50 of a switching relay 51. A call bell 52 is normally bridged across the phantom circuit through the normally closed contacts of a switchin relay 53, normally closed contact 54 of switching relay 5l and normally closed contact 55 of switching relay 48, the bridge including this call bell 52 being connected to one side of the phantom circuit through the windings of retardation coil 56 and with the other 110 side through the win-dings of retardation coil 57. A retardation coil 58 is connected in series with each of the call bells to increase the impedance of the bridge whereby the several bridges are made of high im- 115 pedance to talking currents.

The cord circuits D employed at the intermediate switchboards are of the universal type, so that they may be used for interconnectinglocal common battery telephone l2( lines terminating thereat, or 'for connecting a telephone line with either of the trunk lines or the phantom circuit, or for connecting either of the trunk lines or the 'phantom circuit withatelephone line. Each 125 end of the cord circuit D is similarly equipped. The apparatus associated with the left end oie the cord circuit will be designated by reference numbers without primes and corresponding apparatus associated 13o with the right end of the cord circuit will be designatednwith the same reference numbers with primes.

fr relay is normally bridged across the talking strands and may be energized by ringing current incoming to the intermediate station when the cord circuit is connected with either` a trunk line or a phantom circuit. Each end is also provided with a supervisory relay 8l which functions to control a supervisory lamp 82 on common battery connections, and coperates with the bridged relay 8O when controlled over either of the trunlr lines or the phantom circuit to maintain a locking circuit through the lamp 82, for purposes of supervision. A relay 83 in each end of the cord circuit for controlling a contact in the circuit of the supervisory lamp 82 operates when the cord circuit is connected with either a telephone line, a trunk line or with the phantom circuit. ln series with the relay 83 is a marginal relay Se which operates when connected in circuit with the low resistance 39 of the common battery telephone line, but does not operate when connected in circuit with the high resistance oi' the various sleeve relays associated with the connecting jacks of the trunk lines and the phantom circuit. Each end of the cord circuit is equipped with a ringing key 85, and a listening lrey 63 is provided by means of which the operators telephone set may be connected in circuit.

It plug 60 of the cord circuit is connected with the telephone line C, relays 83 and 84 operate. lf the receiver is ofi' the switchhook the supervisory relay Sl is operated, preventing the lighting of the lamp 82. The restoration or"A the receiver to the switchhoolr causes the lamp 82 to be lighted over a circuit from battery through the lower alternate contact of marginal relay 84, normal contact of supervisory relay 8l, contact of relay 83, and upper normal contact of listening lrey 63 to ground. It the plug 60 is connected with the connecting jack of either a trunk line or the phantom circuit, relay 83 operates, but marginal relay 84 does not operate. rfhe energization of the bridged relay 80, by ringing current incoming to the intermediate switchboard, causes the operation of supervisory relay 8l over a circuit from battery through the winding of relay 8l, contact S6 of relay 8l, resistance 87, contact of bridged relay 80, contact of relay 83, lamp 82 and the upper normal contact of listening key 63 to ground. Relay 81 in operating connects its alternate Contact in bridge ot the contact ot relay 80, thereby establishing a locking circuit for relay 8l. The lamp 82 is maintained lighted over this circuit until the listening key 63 is actuated or relay 83 released. rlhe apparatus associated with the other end of the cord circuit functions in identically the same manner when the plug 62 is employed to connect a cord circuit with a telephone line, a trunlr line or the phantom circuit.

lf the operator at an intermediate switchboard desires to establish a connection over the trunk line 5 in the direction of the terminal switchboard A, the plug 6() of the cord circuit D is first inserted into the jack 36 and the listening key 63 is actuated in order that the operator may determine whether this trunk line is idle or busy. lf found to be idle, the plug 60 is withdrawn from the j ack 36 and inserted into the j acl; 30, whereupon sleeve relay 6l is operated over a circuit from battery through the winding of marginal relay 84:, the winding o1"- relay 83, sleeve contacts of the plug 60 and the jaclr 30 and the winding of relay 6l to ground. Switching relays 20 and 23, 2l and 27 and 48 and 5l thereupon operate. The operation of switching relays 20 and 23 interrupts the normal continuity ot' the trunk line 5 and connects the respective sections or this trunk line to the windings of the repeating coils l() associated with the jacks 80 and 3l. The continuity of this trunk line 5 is not restablished because the normal contacts of jaclr 30 are opened when the plug 60 is inserted therein. The operation of switching relays 2e and 27 interrupts the normal continuity of the trunk line 6 but immediately restablishes the continuity thereot by way of the repeating coils 40 and the normal contacts of the associated jacks 32 and The operation of switching relay 48 disconnects the call bell /l from the looping conductors 2l and 22 and bridges it across that end or" the trunk line 5 which extends toward the switchboard B, while the operation of the switching relay 5l disconnects the call bell 'from the looping conductors 25 and 26 and connects it across the conductors joining the 'windings of the repeating coils e() associated with the trunk line 6. lt will be seen, therefore, that the call bell i6, through the operation of switching relay 5l is bridged across the trunk line 6. The operation oi the switching relays 4S and 5l also connects the phantom circuit call bell 52 in bridge of conductors G6 and 69 forming a part of an alternate looping circuit for the phantom circuit established when connection is made with either trunl-z line.

`While the trunk line 5 has been divided into sections as a result of plugging into the jack 30, the continuity of the trunk line 6 ias been maintained, and, as will now more fully appear, the continuity of the phantom is also maintained. The upper leg of the phantom circuit through the intermediate switchboard may be traced from the alternate contacts of switching relay 20 in parallel through the left-hand windings of the connected repeating coil 40 in parallel, conductor 65, upper normal contact of switching relay 42, conductor 66, upper normal contact of switching relay`43, conductor 67, right-hand windings of repeating coil 40 in parallel and the alternate contacts of thel associated switching relay 23 in parallel. Likewise the lower leg of this phantom circuit may be traced from the alternate contacts of switching relay 24 in parallel through the left-hand windings ot the associated repeating coil 40 in parallel, conductor 68, lower normal contact of switching relay 42, conductor 69, lower normal contact of switching relay 43, conductor 70, right-hand windings of repeating coil 40 in parallel and the alternate contacts oi' switching relay 27 in parallel.

After the insertion of the plug 60 into the jack 30, the operator at the desired switchboard may be signaled by actuating a ringing key which impresses ringing current on the trunk line 5 and causes the operation of the call bell 45 at the appropriate intermediate station, or the operation of the relay 14 at the terminal switchboard A. ln signaling an intermediate switchboard a code may be employed in order that the operator at each switchboard may determine whether that particular switchboard is desired and to determine whether the trunk line 5, the trunk line G or the phantom circuit is to be connected with.

It the operator at the intermediate switchboard had desired to make connection with trunk line 5 in the direction oi the terminal switchboard B, the plug 60 would then have been inserted into the jack 3l. Relay 72 would then operate, causing the operation of switching relays 20, 23, 24, 27, 4S and 5l in the manner above described. It connection had been made with the jack 32, associated with the trunk line G, sleeve relay 7 3 associated therewith would then have operated, whereupon the switching relays would function, as previously described, and if connection had been made with the jack 33, sleeve relay 74 would have operated, causing the operation of the same switching relays.

It the operator at an intermediate switchboard should desire to establish a connection over the phantom circuit in either di-I the trunk line 5 but immediately reestablishes it through an alternate path includding the normally closed contacts of the acks 30 and 31 and the windings of the associated repeating coil 40.v Switching relays 24 and 27 also operate to interrupt the normal continuity of the trunk line 6 and to reestablish it through an alternate path including the normally closed contacts of the jacks 32 and 33 and the windings of the associated repeating coil 40. Switching relays 48 and 51 also operate to connect the call bells 45 and 46 in bridge of the respective alternate looping conductors by means of which the continuity of the trunk lines 5 and 6 is maintained. Phantom circuit switching relays 42, 43 and 53 also operate upon the energization of sleeve relay 75. Relay 42 in operating interrupts the continuity of the phantom circuit at its normal contacts and connects that portion of the phantom circuit extending toward the terminal switchboard A with the lett-hand windings of the repeating coil 41, whereby this end of the phantom circuit is terminated at the intermediate switchboard at which connection is made with the jack 34. The operation of the switching relay 43 likewise terminates the portion of the phantom circuit extending toward the switchboard B at the jack 35 of the intermediate switchboard. The operation of switching relay 53 bridges the phantom circuit call bell 52 across the phantom circuit extending toward the switchboard B. It connection had been made with the phantom circuit otjack 35, relay 76 would then operate, causing the operation ot the same switching relays as are operated by the energization of the sleeve relay 7 5 except relay 53, the energizing circuit of which is not established upon the energization of relay '76. ln this case, however, the call bell 52 would be bridged across the phantom circuit extending toward the switchboard A.

From the above description it will be evident that this invention contemplates a system employing two trunk lines upon which is superimposed a phantom circuit, which join terminal switchboards and are looped through a plurality of intermediate switchboards at each ot which is provided apparatus Jfor establishing connection with either of the trunk lines or the phantom circuit in either direction.. Furthermore, it will be apparent that when connection is made with either trunk line in either direction at intermediate switchboard, the continuity oi that trunk line is interrupted at the particular intermediate switchboard and the call bell normally bridged thereacross is connected with that portion extending in the opposite direction and the normal continuity oi the phantom circuit is interrupted but is immediately restablished through an alternate path, and the phantom circuit call bell is also connected across the alternate path. llVhen connection is made at an intermediate switchboard with the phantom circuit in either direction, the continuity ot the through phantom circuit is interrupted and apparatus functions automatically to divide the original phantom circuit into two phantom circuits. In fact, each trunk line may be divided into as many separate trunk lines as there are sections between switchboards and, in a similar manner, the original through phantom circuit may be split up into as many phantom circuits as there are sections between switchboards.

What is claimed is:

1. ln a telephone system, in combination, two trunk lines joining two widely separated switchboards and looped through an intermediate switchboard` apparatus at each terminal switchboard tor phantoming the two trunk lines thereby providing a phantom circuit over the trunk lines between the terminal switchboards, telephone lines terminating at the intermediate switchboard, a link circuit for establishing connection between a telephone line and one of the trunk lines, and means responsive to the connection of the link circuit with one end of a trunk line Jfor interrupting the continuity thereoic between the terminal switehboards and for maintaining the continuity ot the phantom circuit therebetween.

2. ln a telephone system, in combination, two trunk lines joining two widely separated switchboards, apparatus at each switchboard for phantoming the trunk lines thereby providing a phantom circuit between the switchboards, an intermediate switchboard, circuit leads thereatnormally maintaining the continuity of the trunk lines and the phantom circuit, telephone lines terminating at the intermediate switchboard, a link circuit thereat for connecting` the telephone lines 'with the trunk lines, apparatus responsive to the connection of the link circuit with one trunk line to interrupt the normal continuity ot both trunk lines and the phantom circuit, and other circuit leads thereupon rendered effective tor maintaining the continuity of the other trunk line and the phantom circuit. l

3. ln a telephone system, in combination, two trunk lines joining two widely separated switchboards, apparatus at each switchboard for phantoming the trunk lines thereby providing a phantom circuit between the switchboards, an intermediate switchboard, circuit leads thereat normally maintaining the continuity of the trunk lines and the phantom circuit, telephone lines ter- `iinating at the intermediate switchboard, a link circuit thereat tor connecting the telephone lines with the trunk lines, two sets of terminals for each trunk line at the intermediate switchboard normally disconnectedv therefrom, repeating coil connected with each set ot terminals, means responsive to the connection ot the link circuit with one set of terminals of one trunk line tor connecting one end thereof with the associated repeating coil and for interrupting the normal continuity of beth trunk lines and the phantom circuit, and other circuit leads including the repeating coils thereupon rendered effective for maintaining the continuity of the other trunk line and the phantom circuit.

l. ln a telephone system, in combination, two trunk lines joining two widely separated switchboards, apparatus at each switchboard for phantoming the trunk lines thereby providing` a phantom circuit between the switchboards, an intermediate switchboard, circuit leads thereat normally maintaining the continuity et the trunk lines and the phantom circuit, telephone lines terminating at the intermediate switchboard, a link circuit thereat for connecting the telephone lines with the trunk lines and the phantom circuit, apparatus responsive to the connection of the link circuit with the phantom circuit for interrupting the normal continuity of both the trunk lines and the phantom circuit, and other circuit leads thereupon rendered effective for maintaining the continuity of both trunk lines.

5. ln a telephone system, in combination, two trunk lines joining two widely separated switchboards, apparatus at each switchboard for phantoming the trunk lines thereby providing a phantom circuit between the switchboards, an intermediate switchboard, circuit leads thereat normally maintaining the continuity of the trunk lines and the phantom circuit, telephone lines terminating at the intermediate switchboard, a link circuit thereat for connecting the telephone lines with the trunk lines and the phantom circuit, apparatus responsive to the connecting ot the link circuit with the phantom circuit for interrupting the normal continuity of both trunk lines and the phantom circuit, a plurality of repeating coils, circuit leads including the repeating coils thereupon rendered effective for terminating each portion of the phantom circuit at the intermediate switchboard thereby dividing the original phantom circuit into two phantom circuits, and other circuit leads including several of the repeating coils rendered effective upon the response of the apparatus for maintaining the continuity of the trunk lines.

6. ln a telephone system, in combination, two trunk lines joining two widely separated switchboards, apparatus at each switchboard for phantoming the trunk lines thereby providing a phantom circuit between the switchboards, an intermediate switchboard, circuit leads thereat normally maintaining the continuity of the trunk lines and the phantom circuit, a signal receiving device for each of the trunk lines and the phantom circuit normally connected with the circuit leads, telephone lines terminating at the intermediate switchboard, a link circuit thereat for connecting the telephone lines with the trunk lines, switching apparatus responsive to the con- 'nection of the link circuit withone end of one trunk line to interrupt the normal continuity of both trunk lines and the phantom circuit, other circuit leads thereupon rendered effective for maintaining` the continuity of the other trunk line and the phantom circuit, and switching apparatus lfor connecting the signal receiving devices with the other circuit leads.

7 In a telephone system, in combination, two trunk lines joining two widely separated switchboards, apparatus at each switchboard for phantoming the trunk lines thereby providing a phantom circuit between the switchboards, an intermediate switchboard, circuit connections thereat normally maintaining the continuity of the trunk lines and the phantom circuit, telephone lines terminating at the intermediate switchboard, a link circuit thereat for connecting the telephone lines with the trunk lines, switching relays energized upon the connection of the link circuit with one trunk line to interrupt the normal continuity of both trunk lines and the phantom circuit, and other circuit connections including inductive devices for maintaining the continuity of the other trunk line and the phantom circuit.

In witness whereof, I hereunto subscribe my name this 19th day of August, 1918.

RAY S. WILBUR.

In witness whereof, I hereunto subscribe my name this 2 day of Oct., 1918.

WILLIAM H. HARRISON. 

